a. Field of the Invention
The present invention pertains generally to tools and wrenches and more particularly to wrenches that engage the inner surface of a pipe.
b. Description of the Background
In the plumbing trade, it is common to attach pipe together using a pipe thread that is tapered, such as the standard National Pipe Thread. These thread systems are designed so that the taper of the threads force the internal and external threads to seal against each other to effect a seal for the joint. The very nature of this coupling system is such that the plumber will apply as much force as possible to ensure a tight seal for the pipes being installed. Often, a compound or putty is applied to the threads at the time of installation, but this compound can harden over time or the pipes may corrode, sometimes making removal of the pipe much more difficult than the installation.
The use of tapered threads for joining pipes is a standard method for high-pressure pipes such as steam pipes, gas pipes, and pressurized water, just as examples. The tools required for cutting pipe and cutting threads are part of every plumber""s arsenal of tools, since this type of plumbing is used in almost every home, commercial building, and industrial factory.
The plumber will generally install and remove threaded pipe using wrenches that grip the exterior of the pipe when turning. These wrenches fall into two general categories: those with steel or other metal gripping teeth, and those with a compliant webbing.
The wrenches with steel teeth, of which the common pipe wrench is an example, are adjusted to apply a gripping force to the pipe while the pipe is being turned. As the turning force is applied, the grip is increased, and the pipe is turned.
The wrenches with compliant webbing, such as a strap wrench, consist of a metal handle and a piece of webbing, one end of which is attached to the handle. The free end of the webbing is fed around the pipe to be turned and then through a feature in the handle. As the handle is turned, the handle pinches the strap against the pipe and tightens the strap while simultaneously turning the pipe. A strap wrench described above generally does not have the excellent gripping force of the common pipe wrench with steel teeth. The strap wrench takes a considerable amount of time to install and remove from a pipe before and after turning the pipe, especially when compared to a common pipe wrench.
The wrenches with steel teeth that grab the external surface of the pipe to be turned can destroy the external threads especially when short nipples are being turned by the wrench and insufficient unthreaded portions of the nipple are available to grip. Further, external pipe wrenches often leave unsightly and disfiguring teeth marks on the outer surface of the pipe. This is unacceptable for pipe that is, for example, chrome plated and is not hidden from view. An alternative solution to those problems is the use of compression couplings or other types of fittings to join the pipe sections. However, this is more expensive, and a much more time consuming alternative and is often less reliable.
Actual deformation of a thin wall pipe is possible when a common pipe wrench is used to remove an old, rusted section of the pipe. This is due to the crushing action of the opposing steel teeth across the diameter of the pipe. The same crushing of the pipe may occur when using a strap wrench, since the handle of the wrench presses directly on the pipe as it pinches the strap against the pipe.
Further, all wrenches that engage the external surface of a pipe require some amount of room around the pipe to effectively turn the pipe. For some wrenches, such as the conventional pipe wrench, the amount of room can be considerable, and there are others designed for use in a confined space. However, the wrenches designed for confined space often have severe limitations in terms of ease of use and gripping power, and they always require at least some access to the external portion of the pipe.
In addition to the limitation of requiring a considerable amount of room for operation, the common pipe wrench, the strap wrench, and most other devices for turning a pipe are unidirectional in their operation. In other words, the pipe wrench, when being used for turning the pipe, may only turn the pipe in one direction. In order to reverse the direction of turning, the wrench must be removed from the pipe and turned to grip the pipe from the opposite direction, and reinstalled onto the pipe.
External pipe wrenches also have limitations for assembly in production factory environments. In such environments speed is paramount. Since the common methods of turning a threaded component with a pipe wrench are slow and cumbersome, much time is wasted using conventional pipe wrenches. Designers of such articles, realizing the slow and cumbersome assembly of threaded pipe oftentimes revert to other more expensive types of couplings. The cost savings realized in using threaded pipe can be substantial since the threading operation can be simply automated in a machining step that only takes a few seconds for both the pipe and the article receiving the pipe. The cost of a separate coupling, including a fastener to engage the coupling, may be much more expensive than the threaded interface. In addition, the threaded interface may provide a more esthetic result.
For example, the assembly of articles such as furniture that use components that are cylindrical pipes, such a chrome pipes, may be difficult to assemble using standard pipe wrenches, without marring the exterior cosmetic surface. In addition, high-speed production in factories that assemble boilers, sprinkler systems and components, furnaces, and other systems that use threaded pipe can be substantially limited by the use of a standard pipe wrench. As pointed out above, pipe wrenches are slow and cumbersome, require extra room to maneuver and operate and are generally not effective in a high-speed factory assembly production operation.
Various types of internal pipe wrenches solve some of these problems. For example, U.S. Pat. No. 5,207,131 issued to Pool, et al. discloses an oil filter removal tool. The disadvantage of the Pool, et al. device is that it includes springs 44 that bias the jaws of 48, 50 in an outward direction so that the jaws 48, 50 have to be depressed and urged inwardly to be inserted into an oil pan filter cap. U.S. Pat. No. 3,902,384 discloses an internal pipe wrench that has a tapered actuation element that must be adjusted to engage the inner surface of the pipe. Again, this is time consuming and has potentially other numerous disadvantages. Internal pipe wrenches available from BrassCraft have an offset pivot shaft on which a collar is mounted so that the collar becomes offset as the collar rotates around the offset shaft. The offset shaft that causes the collar to become offset and engage the internal portion of the pipe causes the device to be off center so that high speed assembly or disassembly is not achievable using the BrassCraft tools. In addition, the collar constitutes a single piece and does not tend to engage the inner surface of the pipe or nipple well. In addition, the rotatable sleeve must be oriented in a vertically downward position in order to engage a pipe when employed in a horizontal or nearly horizontal position. In that way, gravity can cause the sleeve to rotate in sync to its lowest point to engage the internal surface of the pipe. Since the sleeve has to be at the bottom, this limits the ease of use of the device. Further, in vertical orientations, the BrassCraft device may fail to easily engage the inner surface of the nipple. Further, the sleeve, because of its small size, may deform the pipe and could egg the pipe especially when engaging thin wall pipe. Further, in vertical alignment applications the user""s fingers may have to be used to orient the rotatable sleeve in the correct position in order to insert the brass craft internal pipe wrench.
It would therefore be advantageous to provide a pipe wrench that can securely grip a pipe from the inside without marring the outside, support a thin walled pipe so that the pipe does not deform while turning even under relatively high forces, be compact and able to work in extremely tight spaces, be simple and quick to use and insert, and be universal in direction.
The present invention overcomes the disadvantages and limitations of the prior art by providing a simple and reliable device for engaging the internal diameter of a pipe, tube, rigid conduit or similar object, a drive coupler, etc., all of which should be considered to be included in the term xe2x80x9cpipe.xe2x80x9d By gripping only the internal surface of the pipe, the external surface is left free from marks and the pipe is supported from any deformation. Further, since the handle or other mechanism for turning the wrench can be configured in many different ways, and almost the entire gripping mechanism is located inside the pipe, the space around the pipe that is required to turn the pipe is minimal. The present invention may also be universal in direction (i.e., can be operated in either turning direction without making any adjustments) so that the user does not have to think about the proper orientation prior to use.
The present invention may therefore comprise a wrench for engaging an internal surface of a pipe and turning the pipe in either direction comprising: a shaft that rotates around a center axis, the shaft having at least two cam driving surfaces that are spaced substantially equally from the center axis for transmitting torque applied to the shaft; at least two gripping shells having external gripping surfaces that are cylindrically shaped to substantially match and engage the internal surface of the pipe, the gripping shells further including internal cam follower surfaces that are designed to be engaged by at least two cam driving surfaces on the shaft so that the torque applied to the shaft is substantially symmetrically transmitted to the at least two gripping shells from the center axis so that the gripping shells apply substantially equal force to the internal surface of the pipe and the center axis of the shaft is substantially aligned with a center axis of the pipe.
The present invention may further comprise a method of fabricating a wrench that is adapted to engage the internal surface of a pipe to turn the pipe comprising: providing a shaft adapted to receive a torque to turn the pipe around a center axis, the shaft having at least two cam surfaces that are adapted to transmit torque applied to the shaft; providing at least two gripping shells each having at least one external gripping surface and at least one internal cam follower surface, the external gripping surface adapted to engage the internal surface of the pipe, and the internal cam follower surface being adapted to engage at least one of the cam driving surfaces on the drive shaft; and providing shoulder surfaces that are disposed on the gripping shells that are aligned to engage a butt end of the pipe upon insertion of the wrench into the pipe, the shoulder surfaces causing the gripping shells to at least partially rotate with the pipe when the shaft is rotated as a result of torque applied to the shaft so that the gripping shells expand and engage the internal surface of the pipe.
The present invention may also further comprise a method of turning a pipe comprising: gripping an internal surface of the pipe with one or more gripping shells of a wrench having gripping surfaces that are cylindrically shaped to substantially match and engage the internal surface of the pipe, the gripping shells further including at least one cam follower surface that is adapted to be engaged by cam driver surfaces that symmetrically apply torque to the cam follower surfaces relative to the center axis in a manner that substantially symmetrically moves the gripping shells such that the gripping shells such that the gripping shells expand to engage the internal surface of the pipe so that the pipe is substantially aligned with the center axis; applying a torque in either direction to the cam driver surfaces to cause the gripping shells to substantially symmetrically expand whenever the cam driver surfaces engage the cam follower surface of the gripping shells; and turning the pipe in the direction of the torque.
The advantages of the present invention include time savings, ease of use and the ability to employ the present invention in tight spaces where other devices for turning the pipe could not be used, such as with a standard external pipe wrench. The wrench of the present invention can be employed with a ratchet which saves time and allows the invention to turn pipes in spaces that may be too tight for a standard external pipe wrench. The compactness of the wrench of the present invention, and the fact that the wrench accesses the pipe from a different direction and in a different way than a standard external pipe wrench, allows the wrench of the present invention to be effectively used in situations that are not conducive to other techniques of handling pipes. In addition, the present invention can be used where nipples cannot be accessed by a pipe wrench, or where threads on short nipples cannot be marred in either the loosening or tightening process. Further, the present invention can be used to remove broken off pipes that are threaded into a fitting, which may frequently occur with the use of plastic pipes. Also, standard ratchet extension bars can be used with the present invention to access hard to reach locations to both tighten and loosen pipe. The present invention is simple in design has a few mechanical moving parts and operates automatically to grip the internal surface of a pipe in either direction to allow either tightening or loosening of the pipe. The weight of the jaws or shells of the wrench of the present invention helps the jaws to automatically open and engage the internal surface of the pipe. Further, the resisting inertia of the jaws, due to the mass of the jaws, helps to open the jaws when the cam first starts turning. Further, the wrench of the present invention is designed so that the pipe end engages the face of the shells or jaws of the present invention which generates friction between the pipe and the jaws to help the jaws stay in a stationary position as the cams function to open the jaws. As a result, the present invention is simple and easy to use due to the elegance of the design. Another embodiment of the present device can be used as an alignment device to align pipes for butt end welding. Further, the present device can be used for power drive applications that allows a receptor unit to be driven in either direction.
The present invention can also be used in conjunction with a ring placed on the outside of the pipe to prevent the pipe from ovaling, such as may occur with thin wall pipes, and to maintain the structure and rigidity of a rusted pipe. Another advantageous feature of the present invention is that the shells include depressed regions that provide room for ridges that may typically be formed at the end of cheaply constructed pipes, such as cheaply made nipples. This allows the spline surfaces or other rough surface of the shell to engage the inner surface of the nipple without interference from the ridges that are formed by these cheaply made nipples.
Another advantage of the present invention is that the shoulders at the rear portion of each shell engaging section butt against the end of the nipple which causes the shells to rotate with the nipple and create movement between the shaft and the shells so that the shells engage the inner surface of the nipple. To assist in this function, a frictional surface can be created on the shoulder portions such as serrations, knurling or other frictional surface. As such, the butt end of the nipple engages the shoulder of the shells with a greater coefficient of friction to thereby enhance this advantageous functionality of the present invention. In addition, various types of frictional material can be used on the outer portions of the shell as well as the shoulder portions including serrating, splines, diamond grip surfaces, rubber grip surface, knurling, et cetera. In some applications, even a smooth surface may be advantageous because of the nature of the pipe that is to be turned.